In a conventional control device for an industrial sewing machine, a limited repertory of sewing patterns such as those shown in FIGS. 1(a)-1(e) are stored in a memory. In the drawings, the capital letters A-J represent respective sewing sections (unit sewing patterns) which comprise sewing patterns. For example, the pattern 1 begins with start bar tacking (SBT) which is itself composed of a forward feed section A and a reverse feed section B, and terminates in end bar tacking (EBT) which it itself composed of a reverse feed section C and a forward feed section D, with the interposition of a free sewing section therebetween. In drawings, symbols ".DELTA." represent the points where treadling back is conducted by the operator and "x" the point of automatic thread cutting and the following up-lock of the needle arm. The symbols "O" represent the point of automatic down-lock of the needle arm at the end of the preset number of stitches. In actual practice, the operator first selects one of the stored sewing patterns 1-5 by pressing a proper pattern selection key switch 7 located in a control panel 6, as shown in FIG. 2. Then, the desired number of stitches corresponding to the respective sewing sections of the selected sewing pattern is set by means of a digital switch 8 which is only for selecting the number of stitches located in the control panel. The key switches A-D can set from 0 to 9 stitches, while the rest of the switches E-J can set from 0-99 stitches.
In such a prior art control device for sewing machines, however, since only one sewing pattern and the number of stitches can be pre-programmed at one time, when the job requires a combination of different sewing patterns, say, the alternate combination of the patterns 3 and 4, it it necessary to employ alternate use of different sewing machines having different programs or, alternatively, the resetting of the sewing pattern and the number of stitches by means of the pattern selection key switch 7 and the switch 8 for selecting the number of stitches each time the pattern is changed. In either case, this program changing operation is cumbersome for the operator and is apt to lead to input error, which results in a considerable reduction in operating efficiency. Further, since the number of sewing patterns capable of being programmed is limited, these prior art control devices for sewing machines have not been able to properly meet the demands for a diverse sewing design.